River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative mineralogical analyses 88–89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of ${\text{SO}}_4^{2-}$\$\end{document} and the formation of H2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pHPZNPC of the sediments was ⩽3.5 and their zeta potentials at the sediment-water interface pH (6.9–7.3) varied from −35 to −45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.

Halloysite nanotubes (HNTs) are hollow clay nanotubes in the nanometer size range, made up of double-layered aluminum silicate mineral layers. HNTs represent an extremely versatile, safe, and biocompatible nanomaterial, used in a wide range of applications in biomedicine and nanomedicine. For example, they are used as transporters for the controlled release of drugs or genes, in tissue engineering, in the isolation of stem cells and cancer cells, and in bioimaging. Consequently, the assessment of the biocompatibility of HNTs has acquired considerable importance. In recent years, HNT composites have attracted attention due to their improved biocompatibility, compared to HNTs, suggesting potential for applications in tissue engineering or as vehicles for drugs or genes. In this review, recent advances in the application of HNTs and HNT composites in biomedicine are discussed to provide a valuable guide to scientists in the design and development of viable, functional bio-devices for biomedical applications.

All’Umanesimo non si deve solo un nuovo interesse filologico verso i classici latini e greci, ma anche una rinnovata attenzione nei confronti della Bibbia. Tra quanti meditarono sul testo biblico e lo posero a fondamento del proprio agire si deve annoverare Ambrogio Traversari (1386–1439), monaco camaldolese e umanista. Attraverso l’esame di una sua lettera, indirizzata ai religiosi del proprio ordine a nome del pontefice Eugenio IV poco dopo essere stato elevato alla carica di abate generale, si metterà in luce come il Traversari, nell’esortarli alla vita monastica, fondi il suo operare tanto sulla letteratura patristica, quanto soprattutto sul ricorso alla Bibbia, rispetto alla quale tralascia l’allegoria medievale per essere invece attento a trarre dal dettato biblico un esempio morale per i propri confratelli.

The influence of clay preparation procedure on sorption and hydrolysis of carbaryl (1-naphthyl, A-methyl carbamate) by the reference smectite SWy-2 was examined. For research purposes, reference clays are sometimes used without purification, or more commonly, the <2 μm size fraction is obtained by gravity sedimentation or low-speed centrifugation. We determined that these common methods did not remove all the inorganic carbonate impurities present in SWy-2, and that these impurities caused alkaline conditions in aqueous clay suspensions leading to the alkaline hydrolysis of carbaryl to 1-naphthol. The hydrolytic activity of homoionic K-SWy-2 disappeared once carbonates were eliminated. Two methods were evaluated for preparing K-SWy-2 devoid of inorganic carbonates. In Method A, inorganic carbonates were first removed by incremental additions of a 0.5 M sodium acetate buffer (pH 5.0) until the clay suspension reached pH 6.8, followed by low-speed centrifugation to obtain the <2 μm size fraction; in Method B, the order of these steps was reversed. Carbaryl hydrolysis was used as a probe to determine the effectiveness of the two methods in terms of the removal of carbonate accessory minerals. Homoionic K-SWy-2 obtained by Methods A and B produced near neutral pH when suspended in water and hydrolysis of carbaryl in these suspensions was not evident. In this regard, both clay preparation methods were acceptable. However, there were procedural advantages with Method B, which is therefore recommended for the partial purification of reference clays, as detailed in this paper.

In order to extend the application of magadiite to optical fields (rather than the usual focus on adsorption, catalysis, ion exchange, etc.), a magadiite-CdS (Mag-CdS) composite was synthesized from Na-magadiite by ion exchange. Various techniques were used to characterize the composite. X-ray diffraction results indicated that the Mag-CdS composite retained the host magadiite structure in spite of decrease in the intensity of the X-ray diffraction peak of the host magadiite. The analytical results confirmed the formation of the Mag-CdS composite, along with the modification of the optical properties of CdS by the host magadiite.

The high fission yield and long half life of cesium and strontium make them the two most high-risk products from nuclear fission, so their separation from radioactive wastes is an important step in mitigating their harmful effects. Clinoptilolite, because of its thermal stability, high radiation resistance, and selectivity, was considered as the adsorbent for this purpose. In order to then separate the adsorbent-adsorbate complex from aqueous solution, the clinoptilolite was prepared as a magnetized composite with nanomagnetite. This magnetically modified zeolite enabled the efficient and quick separation of the adsorbent from solution using magnetic separation. The ability of this composite to remove Cs+ and Sr2+ from aqueous solutions was assessed and characterized using X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, differential thermogravimetric analysis, and vibrating-sample magnetometry. Variables such as initial ion concentration, pH, contact time, and temperature in the sorption process were studied and optimized. The maximum adsorption capacities of the composite were 188.7 and 36.63 mg g-1 for Cs+ and Sr2+, respectively. Investigation of the kinetics revealed that the adsorption process onto the composite was quicker than in the case of the zeolite alone. The equilibrium data were analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. The mean free energy of sorption (E) for both ions was in the range 8–16 kJ mol-1, confirming that an ion-exchange mechanism had occurred. Positive ΔH° and negative ΔG° values were indicative of the endothermic and spontaneous nature of the removal of Cs+ and Sr2+. The saturation magnetization of the composite was measured (17.46 Am2/kg), implying fast magnetic separation of the sample after adsorption. The results obtained revealed that the natural Iranian zeolite nanomagnetite composite was a good ion exchanger in the removal of Cs+ and Sr2+.

Late Miocene (Messinian) alluvial and lacustrine deposits characterize the so-called Kızılbayır Formation of the Aktoprak Basin (central Turkey) and consist of conglomerate, sandstone, mudstone, limestone, marl, and dolomite units. These sediments are composed mainly of feldspar, quartz, hornblende, diopside, olivine, serpentine, calcite, and dolomite with subordinate palygorskite, chlorite, smectite, and illite. Studies by scanning electron microscopy indicate that calcite and dolomite show both meniscus and micrite-sparite-type cements, characteristic of both vadose and phreatic zones. Chlorite, smectite, and illite are products of the alteration of the underlying Güney Formation with subsequent transportation by local streams into the Kızılbayır Formation, and therefore these are considered to be reworked materials. Authigenic palygorskite and dolomite formed as a result of the calcretion of mudstone-carbonate units under alkaline conditions, with high Si, Ca, and Mg activity, and low Al, originated from ophiolitic and carbonate units based on the increase in Ni and Co. The paragenesis and textural features of the minerals of the alluvial fan and lacustrine sediments determined in the study area indicate that precipitation probably occurred due to climate fluctuations ranging from arid and semi-arid to wet conditions.

Rapid dissolution of partly amorphized kaolinite in the systems kaolinite + NiCl2, kaolinite + Ni(OH)2, and kaolinite + NiCl2 + Ni(OH)2, at a temperature of 200°C and at pH between 5.3 and 7.4, leads to the precipitation of Ni-poor kaolinite, Ni-rich kaolinite and Al-Ni-serpentine. Identification of the phases was carried out using a combination of X-ray diffraction and transmission/analytical electron microscopy. Ni-bearing kaolinite shows variable morphologies in the systems studied: stacks of kaolinite with relatively small Ni contents and fine-grained curved particles of Ni-rich kaolinite dominate in the Cl-bearing system; spherical particles with a disordered structure and relatively uniform Ni contents (in the order of 0.15 atoms per formula unit (a.p.f.u.)) and platy particles of Al-Ni-serpentine characterize the products formed in the Ni(OH)2-richest systems. The presence of Ni(OH)2 in the systems (with and without Cl) favors the dissolution process as well as rapid precipitation of spherical particles, and the formation of serpentine. A difference from Mg systems studied previously is a well defined phase intermediate in composition between kaolinite and serpentine which originated in the Ni-bearing systems. Increasing Ni content is clearly reflected in the parallel increase in the b cell parameter of kaolinite. The average composition of the coexisting Al-Ni-serpentine is: (Al1.24Ti0.01Fe0.02Ni1.31) (Si1.58Al0.42)O5(OH,Cl)2.

Electro-osmotic consolidation is considered to be an efficient technique for dewatering and consolidation of soft soil. In the present study, four experiments were conducted on a Na-rich bentonite using two reactive electrodes (copper and iron) and two inert electrodes (graphite and stainless steel) to study the transport and exchange behavior of ions during electro-osmotic consolidation. The results showed that the changes in pH and ion contents were limited to the zone close to the electrode due to the buffering capacity of bentonite and the significant reduction in electric current density. The ion concentration profiles indicated that Na+ ions were largely responsible for carrying the pore water to the cathode. The reactive electrodes are better at transporting Na+ ions and therefore induce better drainage than inert electrodes. Ion-exchange reactions occurred between the Cu2+ and Fe2+/Fe3+ ions released and pre-existing Na+ ions in the electrical double layer, causing decreased water adsorption capacity and plasticity index. The swelling and shrinkage characteristics of the bentonite were thus reduced, and electroosmotic consolidation may therefore provide a new way to improve the stability of expansive soils and slopes.

The Eocene Huber Formation, exposed in the CFI Hall mine south of Irwinton, in Wilkinson County, Georgia, displays colored zones that are a consequence of an oxidative weathering front. These zones vary from very light gray (gray) to pinkish white (pink) to very pale yellow (cream) (Munsell N8, 5YR 8/2 and 2.5Y 8/2, respectively) with increasing degree of oxidation. A representative sample from each zone was collected and analyzed for its chemical, crystallographic and Raman spectroscopic properties. The comparison of these genetically related samples allowed for a quantitatively accurate assessment of anatase’s contribution to the total TiO2 content. All samples contain ∼1.5 wt.% TiO2. Progressing from gray to pink to cream, anatase contents range from half to nearly all the TiO2. The a lattice parameter for anatase is constant in all three kaolins (3.7916 Å), suggesting a constant 4.6 mol.% isomorphous substitution of Fe for Ti.

Phase characterization and mass-balance considerations of the gray, pink and cream kaolins indicate that ilmenite and pyrite are precursor Ti- and Fe-bearing phases in the gray kaolin that undergo oxidation. Pseudorutile is a proposed intermediate phase resulting from the anodic corrosion of ilmenite. Hematite, goethite and anatase are the dominant end-products via dissolution-precipitation from the reactants pyrite and pseudorutile. The removal of Fe sulfides and organic matter and addition of hematite and goethite causes kaolin colors to change from gray to pink. Oxygen diffusing from groundwater in permeable overlying and underlying formations facilitates a process that probably involves aerobic and anaerobic bacteria that utilize Fe from pyrite, hematite and goethite. We postulate that the end result is the mobilization of Fe by siderophores and a kaolin color change from pink to cream.

Intercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites.

Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montmorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed — the proportional influence of individual components was found to be more prominent.

The Konya region in central Anatolia is covered by Pliocene-Late Pleistocene sediments and volcanites related to the sediments NNW of Karapınar, Turkey. In the area, the Upper Miocene-Quaternary Üzecek Dağı and Karacadağ volcanites are generally of the same age and formed from magmas of similar composition. The Karapınar formation is brown to whitish-beige, partly fossiliferous and consists of limestone, marl, claystone and, locally, sandy layers. Silica-rich lenses, nodules and layers are observed in the upper strata which locally contain sepiolite-rich layers. The mineralogical composition of sepiolite samples taken from the area was determined by powder X-ray diffractometry, while the abundance of major-element oxides was measured by X-ray fluorescence spectrometry. The crystallographic and morphological properties of samples were determined by means of scanning electron microscopy and energy dispersive spectroscopy. Samples were taken from three sections and from random locations. Mineral assemblages in the same stratigraphic position are generally similar in the three sections, while the thickness of the individual beds varies between the sections. Dolomite and calcite are the main carbonate minerals in the sections. Sepiolite occurs primarily with dolomite and, locally, dolomite and calcite, and less commonly with just calcite. Generally, quartz, feldspar and mica are found, especially in the upper parts of the sections where tuff is abundant. CaO and MgO dominate the major-element oxides. The CaO content is between 1 and 30% while MgO is 3–21%. Al2O3 and SiO2 are generally higher in the sepiolitic and tuffitic layers. Al2O3 is <3% and SiO2 is between 15–18% in the sepiolitic layers. The average structural formula of sepiolite was calculated as: (Mg7.00Al0.44Fe0.18)(Si11.71Al0.29)O30 (OH)4(OH2)4Ca0.13K0.09Na0.01. Sepiolite occurs as fibers and dolomite as subhedral or euhedral crystals. It is considered that sepiolite was formed either by conversion of dolomite or by direct precipitation from solution under alkaline and saline conditions in the Karapınar paleolake. The paleolake was saturated with respect to Mg, Ca and Si derived from groundwater that percolated along fracture systems.

Radiocesium was deposited on the soils of Fukushima Prefecture in Japan after the meltdown of the Fukushima Daiichi Nuclear Power Plant in 2011. The radiocesium bound to 2:1 clay minerals, such as vermiculite, common in the soil of that region and became non-exchangeable due to the strong affinity of these clay minerals for the Cs+ adsorbed. The current study generated adsorption envelopes for Cs+ on three zeolite minerals: zeolite Y, ZSM-5, and ferrierite. Two of these (ZSM-5 and ferrierite) caused monovalent cations to adsorb via a strong inner-sphere mechanism. A comparison of Cs+ adsorption on these zeolites to Na+ adsorption on the same zeolites showed that Cs+ adsorbs much more strongly than Na+, which is explained by its atomic properties. Despite the inner-sphere adsorption of Cs+ on ZSM-5 and ferrierite, the affinity of vermiculite for Cs+ is even stronger. An adsorption envelope for Cs+ on vermiculite failed to show a low-pH adsorption edge even at a pH of 1.01, with adsorption remaining at ~65% of the maximum even at this low pH. The adsorption envelopes for Cs+ on ZSM-5 and ferrierite minerals did show low-pH adsorption edges centered at pH 3.5 and 3.0, respectively, where Cs+ adsorption dropped to zero. The greater affinity of vermiculite for Cs+, even when compared with that for two zeolite minerals known to have significant affinities for monovalent ions, highlights the difficulty in removing Cs+ from contaminated Fukushima soils.

Particle concentration, charge, solution chemistry (i.e. ionic strength), and the nature of organic matter (OM) are the major factors controlling particle flocculation in aqueous environments. In the present study, the nature of clay fabric associated with clay—OM interaction at a range of ionic strengths was the focus. In the flocculation experiments, the aqueous suspension of montmorillonite and chitin was mixed with NaCl/MgSO4 electrolyte solution. Advanced sample-preparation techniques and visualization methods using transmission electron microscopy were used to observe directly the micro- and nano-scale clay—OM fabric of the resulting flocs. Such direct observation elucidated the role of OM in clay flocculation; few attempts have been made in the past due to the technical difficulties in preserving the original structure. A comparison of clay fabric at two different ionic strengths of 0 and 0.14 M revealed that the individual hexagonal clay particles settled slowly with little intra-aggregate void space (void ratio: 0.07) at 0 M while rapid flocculation and settling of clay particles at 0.14 M, with or without OM, resulted in a more open fabric with greater void space (void ratio: 0.33). The silver-staining technique demonstrated effectively the location of electron-transparent chitin in montmorillonite aggregates. Chitin appeared to link the face-to-face (FF) contacts of clay domains by bridging between negatively charged face surfaces. However, the resultant void ratio and the average hydrodynamic diameter (dH) values were lower than in the OM-free system after flocculation. The results indicated that the interplay between ionic strength and OM content affected the floc architecture and void ratio.

This article investigates the sonic and spatial properties of “evangelical” experience in the eighteenth-century South. Utilizing an array of manuscript letters and diaries, I argue that, while scholars have explained the intellectual convictions responsible for Southern revivalists’ democratic impulse, we must also acknowledge the equally formative role of space and sound. By highlighting how upper-crust whites racialized space and sound in the unawakened South, this article shows that, as revivalists popularized loud, open-air practices, they actively redefined Christian experience in spaces and sounds long-defined as Indian, Black, and lower-class. In doing so, New Lights couched their movement in a radically new sensorium that distinguished them from entrenched ecclesial bodies and empowered would-be followers to, as the South Carolina Baptist Edmund Botsford put it, “think & act for your selves.”